An entire space mission on paper?

[Der Anfang]

Let's say I want to go to the Mun launching from Kerbin. However, I want to challenge myself by flying mostly IVA and writing down all of my information and a "road map" ahead of time. No using the map mode, and most especially no Maneouvre nodes. Is this possible? In real life, astronauts obviously don't have a "map mode", lol, but I am wondering if there are any technical limitations to ksp that would make it almost impossible. If not, what formulae would I require for a Mun Flyby (or even a Mun Landing)? What do I need to know? I think Kerbal Engineer and Mech Jeb are obvious no-noes.

Please, anybody who might know, provide details.

EDIT: The first poster who replied to this pointed out that using map mode in ksp is the equivalent of a mission control, which real life astronauts use, I'd assume. But what I am looking for more is the actual math behind it all, and how it's done.

Edited September 26, 2015 by Der Anfang

[Nothalogh]

astronauts obviously don't have a "map mode"

Sure they do, it's called mission control

[Der Anfang]

Sure they do, it's called mission control

I... I... touché. I think I meant more though not a direct visual of what your trajectory looks like and such. Obviously there is a lot more math involved. How are those arcs calculated, etc. That's what I meant by that.

Okay... perhaps I should reword my post, shouldn't I?

Edited September 26, 2015 by Der Anfang

[Zephram Kerman]

Sorry I don't have much useful advice to answer your actual question. It's one of those, "Simple question, big bad complicated answer" type things.

But, I just have to comment, your thread subject made me think of that one time I was in the KSC cafeteria with Bob and Bill joking about flying a spaceship to Duna. I showed them the yellow sticky, then Bill started sketching on the napkin. And the rest, as they say, is history.

[Phil deCube]

In real life, astronauts obviously don't have a "map mode"

In real life, astronauts used a computerised autopilot. http://history.nasa.gov/computers/Ch2-1.html

[GoSlash27]

Der Anfang,

You can do most of it on paper and don't need to use maneuver nodes at all, but there are some situations where you'll have to refer to the map at least temporarily.

For example, you need to verify your periapsis when you cross SoI boundaries to ensure that you're not going to smack into the surface or miss the atmosphere on the way back. For safety's sake you need to at least verify in map mode that your burn has gone as predicted.

Also it is the only way you can see your ship information tab. You need that from time to time during the mission.

For mission planning you use the vis-viva equation https://en.wikipedia.org/wiki/Vis-viva_equation

For stage design you'd use the reverse Tsiolkovsky rocket equation http://forum.kerbalspaceprogram.com/threads/102809-The-reverse-rocket-equation-explained

This resource is excellent:

http://www.braeunig.us/space/orbmech.htm

Best,

-Slashy

Edited September 26, 2015 by GoSlash27

[GoSlash27]

AFA how,

Stage 1 is planning out the mission. It is assumed that you know what the aero losses are during launch to LKO so you have that part of the DV budget already figured out.

1a) Planning the launch to Munar orbit from the surface. We'll pick an altitude arbitrarily.. say 10km.

We already know the Mun's mass and sea level radius. From this, we can compute what our orbital velocity would be at the surface.

v= sqrt(GM/r) where M is the Mun's mass in grams and r is the Mun's radius in meters.

G is the universal gravitational constant; 6.67408 × 10^-11

^{Plugging in the Mun's mass and radius gives us 571 m/sec.}

^{Extending the apoapsis to 10km using the vis-viva (step by step process in the "orbmech" link I posted) shows that you need another 7 m/sec. Circularizing at 10 km requires yet another 7 m/sec.}

^{It would therefore take an absolute minimum of 585 m/sec DV to get from the Munar surface to orbit and you'd want to pad that figure to account for gravity losses, cosine losses, and imperfect flight path. Probably 20% will be fine for launch, but you'll want to be extra generous for landing DV, perhaps even doubling it.}

^{So we'll design our Munar lander for 700 m/sec DV for launch and 1,150 m/sec DV for landing.}

^{We know from the vis-viva some important figures we'll want to remember for future use: Orbital velocity= 557 m/sec. Velocity to set periapsis to sea level= 550 m/sec Velocity to set apoapsis to 10km during launch= 577m/sec}

[GoSlash27]

1b) Designing our Munar ascent stage.

Before we begin this, we need to know one more thing about the Mun: What's the surface gravity (g)?

g=GM/r^2

The Mun's surface gravity is therefore 1.63m/sec^2

We will pick a reasonable minimum acceleration in "g"s. 1g exactly will no doubt be wasteful of fuel and gobs of acceleration will be difficult to control with precision and sacrifices lightness for moar boosters. We'll go with 1.2g

q#1: if I were to build a rocket using just 1 of my proposed engines, how much mass could it lift at 1.2g Munar?

a: M= T/(1.2*1.63) where M is in tonnes and T is in kN. A single LV-1R could lift up to 1.02 tonnes total mass on the Mun at a minimum of 1.2G.

q#2: How much of this mass would have to be fuel in order to generate 700 m/sec DV?

a: Using the reverse rocket equation, we know that our wet-to-dry ratio (which I'll refer to as Rwd) needs to be e^(DV/(9.81Isp)), 1.25.

We know that our fully fueled rocket will weigh 1.25 times as much full as it does when empty. Converting this to fuel percentage, we subtract 1 and then divide it into the fully fueled portion. .25/1.25= 1/5= 20%.

We know that our fuel tanks weigh 1/8 as much as the fuel they contain, so fuel tanks account for 2.5% of our mass.

q#3: How much of this theoretical lifter would be payload?

We take our total mass and then subtract the mass of the engine, fuel, and tanks.

Mp= M-Me-Mf-Mt

1.02-.02-1.02(.2+.025)= .77 tonnes.

A theoretical rocket using one of these engines could place .77 tonnes into Munar orbit. We can repeat this process with several different candidate engines.

We need to know how much payload we actually need to place into orbit. We'll need a lander can, docking port, RCS quads, perhaps a battery and solar panels. Say that weighs about a tonne.

This is just a little more than 1 of these engines can handle, but 2 can do it no problem. So now we design it for real.

Rwd= 1.25

Referring to my "reverse rocket equation",

(Rwd-1)(NMe+Mp)/(9-Rwd) will give you the mass of your empty fuel tanks.

N= number of engines (2)

Me is the mass of your engine (0.02)

Mp is the mass of your payload (1)

So our tank weighs .03t when empty. Fill it with LF&O and it weighs 9 times as much; .302 tonnes.

So that's it. Our 1 tonne ascent module, .302t of fuel tankage, 2 LV-1R engines.

This comes out to 1.34t total mass. This whole assembly now becomes payload for the descent stage.

- - - Updated - - -

So now that I've gone into detail for the ascent stage, I won't bother repeating it for the other stages of the mission. It's the same procedure.

Our ascent stage (plus decoupler) is payload for the descent stage. It needs to make 1150 m/sec at a minimum of 1g Munar with a payload of 1.4tonnes.

A single 48-7S will do this with a total mass of 2.51 tonnes.

The Munar lander is, in turn, payload for the Munar transstage.

In a parallel fashion, you have to work out your trip home using the CM with reentry capsule.

These are both payloads for the TMI stage, which is payload for the upper transstage, which is payload for the booster.

In working out the transstage, we again use the vis-viva to get us an apoapsis at the Mun's altitude. One important thing to note is the period of this orbit, because we actually have to arrive at the Mun. Likewise, we need to know the Mun's orbital velocity around Kerbin so we can work out how much to lead it by. This is all in the "Orbmech" reference.

Happily, it works out that the Mun is ideally situated when you see it rise above Kerbin's surface. And you've already worked out what your velocity will be when it's time to cut engines.

Apologies for the wall o' text, but this should be enough to get you going.

A couple more points to add that should prove helpful: If you know your current mass, engine Isp, and fuel/ o2, then it's a simple matter to compute your remaining DV to make sure you're not in trouble. each 90 units of fuel and 110 units in the tank *of the current stage* is a tonne.

current mass/(current mass-fuel mass) = Rwd

9.81xIspxln(Rwd)= DV

You want to keep track of this throughout the mission. You probably want to get into the habit of doing an "around the horn" check before each burn in order to be safe.

If you know your current mass, engine thrust, and DV of the burn, you can compute the burn time. Handy to figure this out ahead of each burn.

Good luck!

-Slashy

Edited September 26, 2015 by GoSlash27

[MarvinKitFox]

.... But what I am looking for more is the actual math behind it all, and how it's done.

I suggest you start with:

bone up on some:

and a smattering of

Or alternatively, if you prefer the hands-on approach, go the Scott Manley way:

[Der Anfang]

The responses here are great. Hahah, I love you all. Thanks. This is all very interesting!

[Nothalogh]

This all gives me an idea, what if multi-player in KSP involved an actual mission control?

Anyone who has played Artemis knows what I'm getting at

[GoSlash27]

This all gives me an idea, what if multi-player in KSP involved an actual mission control?

Anyone who has played Artemis knows what I'm getting at

Nothalogh,

I've never played Artemis (or even heard of it for that matter) but I think I see what you're getting at. I'm not sure which position on the team I'd be best- suited for. I'm sort of a "jack of all trades" in KSP but there's somebody out there who's better in any specialized role.

Best,

-Slashy

[Nothalogh]

Nothalogh,

I've never played Artemis (or even heard of it for that matter) but I think I see what you're getting at. I'm not sure which position on the team I'd be best- suited for. I'm sort of a "jack of all trades" in KSP but there's somebody out there who's better in any specialized role.

Best,

-Slashy

Artemis is a scifi styled spaceship bridge simulator, each player handles a particular job within the crew.

It requires like six or so people, Captain, Comms, Navigation, Weapons, Sensors, Damage Control, etc.

They all are interdependent, and must communicate amongst each other to achieve the objective